The choice of which language strategies to use in schools in Africa is the subject of much debate. In the Life Sciences, cultural issues associated with the use of biological terminology add to this debate. In our study, we examined the language choices made by Grade 7 Natural Sciences teachers in South Africa during their teaching of human reproduction. A mixed method approach was employed, involving firstly a survey questionnaire amongst 40 teachers in urban schools followed by a multiple case study of 10 of these teachers. Data were collected during classroom observations by means of field notes and audio-recordings followed by interviews which were transcribed and coded. We found that teachers used a variety of language strategies including use of home languages, English or code switching. The teacher's and/or learners' fluency in English and the teacher's perception of the need for learners to feel at ease when discussing human reproduction influenced their choices. In addition, teachers' belief in the importance of using biological terminology rather than traditional metaphors in order to create a more formal and thus respectful discourse, led them to use the English version of the biological terms. We argue that different language choices are appropriate for different urban contexts, and that teachers should use the language/s in which learners are most comfortable in order to enable deep and rich discussions on the sensitive subject of human reproduction.